I'm not sure that this falls under the subsistence allowance category or even the FIA category; I wouldn't put it past DIO Ops(Accn) to have (or indeed invent) some other form of compensatory payment outside of the allowances package.
Slightly off topic but I'm having a minor 'discussion' with DIO at the moment who have taken the viewpoint that the relevant JSPs don't apply to them (but are happy to quote them at me).
I had one of their reps tell me they don't work to the JSP when having a discussion about some of the things I felt should be provided in my home. I asked him to provide me with the rules and regs they did work to and he agreed to send them to me as soon as he got back to the office. That was three years and one posting ago, I sometimes wonder if he ever got back to the office because the lying **** never sent me his mythical rule book funnily enough.